P.H. D. Thesis

 The thesis Defense session of Mr Akbari,Hassan with the title of“ Analytical investigation of the relation of physical characteristics of urban streets and environment sound indices ” under supervision of Dr.M,Abbaszadegan and Dr.M.Sepehri ,will be held in 13 of January 2013 at 16:00 Pm in School of Architecture and environmentaldesign.

  Abstract

  Streets and squares are the important elements of urban environments, and their acoustic conditions and acoustic comforts are receiving great attention with increased city center regeneration. The purpose of this thesis is to investigate the effects of architectural changes and urban design of street facades’ on the sound propagation and also to achieve desirable design approach street facades from the acoustical point of view.

  The research methods used in this study is a combination of experimental method and simulation . The first is based on experimental methods . At this point, Based on background traffic noise levels and the physical characteristics of the street, the case study be chosen . Then the dependent variables are measured and examined in a real environment with acoustical devices and specialized software . At the next step, after review ing the validity and reliability of software, the effect of physical variables on the sound indices has been studied using a simulation approach . Intervention at current situation was done by simulation approach and based on solving systems of equations using combinations method e.g. “Ray tracing method”, “Image Source method” and the “Lambert Cosine law “. In this research, the effect of physical characteristics e.g.” the longitudinal and height distance of the source -receiver, projection and dent on facades, the form of skyline, aspect ratio of street, architectural insertion (porch and balcony) and absorption-scattering coefficient” on sound indices e.g. ”sound pressure level, reverberation time and early decay time” has been investigated.

  The results indicate that physical variables such as” projection on facades, the increase of reflexive surface area at the center of façade, architectural insertions (porch and balcony), the increase in aspect ratio and decrease in absorption-scattering coefficient of materials" cause an increase in the value of reverberation time, early decay time and sound pressure level in urban streets. Also physical variables such as“ dent of facades, decrease in reflexive surface area at the center of façade, decrease in aspect ratio and increase in absorption-scattering coefficient of materials” cause a decrease in the value of reverberation time ,early decay time and sound pressure level in urban streets.

  Keywords :

  street facades, acoustic simulation, reverberation time , early decay time , sound pressure level